Heater



FIG. 1 is a front perspective view of a heater showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side view thereof; and,

FIG. 4 is a front view thereof.

The broken line shown in the drawings are for the purpose of illustrating portions of the article and form no part of the claimed design. 

CLAIM The ornamental design for a heater, as shown and described. 